400 amp electrical service: who needs it

Check the load before you pick the size

A 400 amp service is a big step up, and most people who ask about it do not need it. The size of a service is set by a load calculation, not by how many appliances a house has. The electrician adds up the square footage, the small-appliance and laundry circuits, fixed appliances, heating and cooling, and any EV charger. The code then applies demand factors, because everything is never on at once. If the result is under 200 amps, 200 amps is the answer. The load calculation guide shows the steps.

When the total passes 200 amps

The homes that land at 400 amps tend to look like this:

• 3,500 square feet or more, with electric heat or a heat pump on each floor,
• an ADU or guest house sharing the main service,
• a pool or spa, with its pump, heater and lights,
• two or more Level 2 EV chargers running at once,
• an electric range, electric dryer and electric water heater.

Even then, there are ways to stay at 200 amps. A smart panel or a charger that shares power can cap the load. The 2023 NEC lets an energy management system limit the load on a service in some cases. Whether your inspector and utility accept that is a local call, so ask before relying on it.

What changes at 400 amps

The service is bigger in every part.

Part	What changes
Service conductors	Heavy copper or aluminum, sized for 400 amps
Conduit and mast	Larger. One city chart lists 400 kcmil conductors in 2-1/2 inch conduit
Grounding	A larger grounding electrode conductor, 1/0 AWG in that same chart
Meter	A larger socket, and possibly a different meter type
Panels	One 400 amp panel, or a disconnect feeding two 200 amp panels
Utility	May need a bigger service lateral or transformer

The chart is from Laguna Niguel’s January 2026 handout. Your city and utility set their own tables, so treat these as examples.

The utility is part of the job

The meter and the lines up to it belong to the utility. For 400 amps, the utility planner reviews the request and decides what its side needs. That might be nothing, a larger service lateral, or a transformer change. SCE, SDG&E and LADWP each run their own process, and each reply sets the schedule. Do not assume a date until the utility has answered. The utility coordination guide explains how the planner step works, and the meter and service mast page covers the equipment on your side.

Timing is where this job differs most from a 200 amp swap. A swap is often a one-day job. A 400 amp upgrade can take weeks or months when the utility has to build something. No fixed lead time is published for house service upgrades, so ask your utility planner.

Cost

The typical SoCal range is $8,000 to $12,000 as of October 2026. It includes the 400 amp service, the meter socket and the panel or panels. It does not include utility fees, trenching for an underground lateral, stucco or landscape repair, or a new circuit run to a far outbuilding. Read the 400 amp cost page for the factors, and try the cost estimator for a first number.

Permit and inspection

A 400 amp service needs an electrical permit and a city inspection. Many cities also want to see the utility service order before they issue the permit. Plans often include a single-line diagram showing the service, the panels and the load calculation. The permit and inspection page covers the steps.

Surge protection and disconnect

A new 400 amp service for a house also needs a Type 1 or Type 2 surge protective device under section 230.67, and an outdoor emergency disconnect under 230.85 on one- and two-family homes. California’s 2025 Electrical Code took effect January 1, 2026 and is based on the 2023 NEC.

Questions to ask the electrician

1. What load calculation supports 400 amps, and can I see it?
2. Would a smart panel or load sharing keep me at 200 amps?
3. Which utility steps are included, and who schedules them?
4. Is the quote for one panel or two, and where do they mount?